"It was disarray," Houston said. "All the lights were out. It was pitch black. ... I think it was still burning in that corner."

Plant worker Nate Lewis, 21, said he was on the first floor when he heard the blast. The building went dark, so he used light from his cellphone to make his way across the production floor to safety outside.

"I was a production line worker, although I don't know if I want to be that anymore," said Lewis, who's worked at International Nutrition for about four months.

The plant sits in an industrial area visible from Interstate 80, which bisects Nebraska's largest city. There are no residences nearby and no other buildings were evacuated after the explosion.

Jamar White said he heard a loud crack and then looked up to see the back wall of the building collapsing.